There are bristle worm traps or you can catch them at night with tweezers or something similar. The bristles will stick you like fiberglass. They wont harm fish or corals. Most that remove them just dont like the look of them. Probably came in your live rock. I got some with a Green Star Polyp that I bought on craigslist.
over feeding can cause a population explosion, of bristle worms and then when you correct the over feeding they will die off and that can be an ammonia problem. I have several in my tank at the present time, with no problems. I have been told that they may kill clams by eating their way in thru the clams foot. I have not experienced this so far. have had a clam in the tank with the worms for over a year. I consider them an important part of the CUC
I have one that lives around a colony of Zoos, and since then these zoos will not open. It could be unrelated. In this colony of zoos there are green and pink ones. The green ones are growing fast, and the pink ones barely open.
That's proof that it's not the worm then. I don't know what the zoas that are unhappy are not getting. I've heard that some like more light than others, and some are much slower growing than others. I don't keep them, so I can't help you more than that.